I can only suggest looking at EBay for anything. I also go to Messick’s for parts and such, but not sure what the price would be for you there. We have found smaller items on EBay, for our SVL75-2 , like latches, etc. good luck.
edited to add: not sure what price you are seeing for your door, but just found a website selling Lexan instead of glass for skidsteers. The website is www.shieldswindshields.store. I saw for Kubota it ranged from $411 to $579. You’d have to see if that was acceptable and the difference in price if that would be something you wanted to check out. Not sure if the frame is included. Again, good luck!